The present invention relates to a fuel supply apparatus of an internal combustion engine. More particularly, the present invention relates to an engine that can be used for a model airplane.
In the conventional fuel supply apparatus for supplying fuel to the combustion chamber of the engine which is used for the model airplane, the mixing of air and fuel is adjusted in a carburetor, and the mixture of the air and the fuel is fed to the cylinder from the air supply path. The amount of the fuel is adjusted by the needle valve of the carburetor.
In the conventional carburetor, a necessary amount of fuel is not supplied in correspondence to a large amount of air sucked into the carburetor when the number of rotations of the engine is increased rapidly from a small number of rotations thereof. That is, the air-fuel ratio is unbalanced.
Consequently, the rotation of the engine becomes nonuniform. Further the fuel is not supplied to the carburetor appropriately owing to a centrifugal force generated during flight of the model airplane. Therefore, the engine has a bad condition in its drive.
In the case where the fuel is injected at a position apart from the air supply valve, the fuel vaporizes before it is sucked into the carburetor and heat is robbed from the peripheral space. As a result, the air-fuel mixture gas expands and the volume efficiency deteriorates. When the fuel has entered the combustion chamber, it is impossible to cool the combustion chamber because the fuel has already vaporized. When the fuel is injected successively by using a gear pump or a plunger, the fuel is injected even when the valve is closed. In this case, there is a possibility that the fuel collects on the closed valve. In this case, when the valve is opened, the fuel which has collected on the closed valve may enter the combustion chamber. Consequently, the fuel does not vaporize appropriately. In the case where the gear pump or the plunger is used, the fuel is supplied according to the number of rotations of the engine. Therefore, as the number of rotations of the engine becomes higher, a supply pressure becomes increasingly high.
The present invention has been made to solve the problem. Therefore, it is a first object of the present invention to provide an engine having an improved response and allowing a combustion chamber to be cooled efficiently when fuel vaporizes.
It is a second object of the present invention to provide an engine having an improved response and allowing a combustion chamber to be cooled efficiently when a fuel vaporizes, by so constructing the engine that intermittent injection of a proper amount of fuel can be accomplished.
The first object described above is attained by an engine of a type in which an air supply valve of a cylinder is opened and closed by rotation of a crankshaft which is transmitted to an air supply cam and an air supply push rod. The engine has a fuel supply system comprising a fuel pump provided with valves for opening and closing a fuel suction hole and a fuel exhaust hole alternately, synchronously with a movement of an air supply push rod, a pipe connecting said fuel suction hole of said fuel pump and a fuel supply source to each other, and a pipe connecting said fuel exhaust hole of said fuel pump and a fuel injection device provided on an air supply port of the cylinder to each other, wherein a fuel is fed to said fuel injection device from said fuel pump owing to an upward movement and a downward movement of said air supply push rod caused by a rotation of said crankshaft; and said air supply valve is opened to inject said fuel.
Also, the first object described above is attained by an engine of a type in which an air supply valve of a cylinder is opened and closed by rotation of a crankshaft which is transmitted to an air supply cam and an air supply push rod. The engine comprises the cylinder having an air supply port, a fuel injection device provided on the air supply port of the cylinder, a fuel pump having a fuel pump chamber, a fuel suction hole and a fuel exhaust hole both communicating with said fuel pump chamber, a piston member for setting an inside of said fuel pump chamber to a pressurized state and a depressurized state according to a movement of said air supply push rod, a lead valve for opening said fuel suction hole when the inside of said fuel pump chamber has the depressurized state, and a lead valve for opening said fuel exhaust hole when the inside of said fuel pump chamber has the pressurized state, a pipe connecting said fuel suction hole of said fuel pump and a fuel supply source to each other; and a pipe connecting said fuel exhaust hole of said fuel pump and said fuel injection device to each other.
The second objects described above is attained by an engine of a type in which an air supply valve of a cylinder is opened and closed by rotation of a crankshaft which is transmitted to an air supply cam and a air supply push rod for an air supply valve. The engine comprises a crankcase having an air supply pipe, the cylinder having an air supply port including an air-feeding pipe connected to an inside of said crankcase, a fuel injection device provided on the air supply port of the cylinder, a fuel pump having a valve for opening and closing a fuel suction hole and a fuel exhaust hole synchronously with a movement of said air supply push rod for said air supply valve, a pipe connecting a fuel suction hole of said fuel pump and a fuel supply source to each other, a fuel supply pipe connecting a fuel exhaust hole of said fuel pump and said fuel injection device to each other, and a fuel supply regulator provided in said fuel supply pipe to adjust an amount of a fuel in such a way that the higher an internal pressure of said crankcase or that of said air-feeding pipe is, the more an amount of said fuel becomes.
Also, the second objects described above is attained by an engine of a type in which an air supply valve of a cylinder is opened and closed by rotation of a crankshaft which is transmitted to an air supply cam and a air supply push rod for an air supply valve. The engine comprises a crankcase having an air supply pipe, the cylinder having an air supply port including an air-feeding pipe connected to an inside of said crankcase, a fuel injection device provided on the air supply port of the cylinder, a fuel pump having a fuel pump chamber, a fuel suction hole and a fuel exhaust hole both communicating with said fuel pump chamber, a piston member for setting an inside of said fuel pump chamber to a pressurized state and a depressurized state according to a movement of said air supply push rod for said air supply valve, a lead valve for opening said fuel suction hole when the inside of said fuel pump chamber has the depressurized state, and a lead valve for opening said fuel exhaust hole when the inside of said fuel pump chamber has the pressurized state, a pipe connecting said fuel suction hole of said fuel pump and a fuel supply source to each other, a fuel supply pipe connecting said fuel exhaust hole of said fuel pump and said fuel injection device to each other, and a fuel supply regulator provided on said fuel supply pipe and having a diaphragm partitioning an inside of said fuel supply regulator into a primary side communicating with a fuel inflow port, a fuel outflow port, and a fuel return hole and a secondary side communicating with an inside of said crankcase or an inside of said air-feeding pipe and moving when there is a pressure fluctuation at said secondary side; and a valve, for said fuel return hole, capable of adjusting an open degree of said fuel return hole owing to a movement of said diaphragm in such a way that the higher a pressure at said secondary side, the lower the open degree of said fuel return hole becomes.